88 DISEASES OF CATTLE. 



A bluish or blue mucous membrane indicates that the blood is 

 imperfectly oxidized and contains an excess of carbon dioxid, and 

 is seen in serious diseases of the respiratory tract, such as pneumonia 

 and in heart failure. 



The secretions. — The secretions may be either diminished, in- 

 creased; or perverted. In the early stage of an inflammation of a 

 secretory organ its secretion is diminished. In the early stage of 

 pleurisy the serous membrane is diy, and as the disease advances the 

 membrane becomes unnaturally moist. The products of secretion 

 are sometimes gi-eatly changed in character from the secretion in 

 health, becoming excessively irritant and yielding evidence of chemi- 

 cal and other alterations in the character of the secretion. 



Cough. — Cough depends upon a reflex nervous action, and may be 

 primai"y Avhen the irritation exists in the lungs or air passages, or 

 secondary when due to irritation of the stomachy intestines, or other 

 parts having nei-^ous communications with the respiratoi-y apparatus. 

 A cough is said to be dry, moist, hai-sh, hollow, difficult, paroxysmal, 

 suppressed, sympathetic, etc., according to its character. Cough is 

 a very important symptom, often being diagnostic in diseases of the 

 respiratory organs ; but this is a subject which can be more satisfac- 

 torily treated in connection with the special diseases of the organs in 

 question. 



Respiration. — In making an examination of an animal observe the 

 depth, frequency, quickness, facility, and the nature of the respira- 

 tory movements. They may be quick or slow, frequent or infrequent, 

 deep or imperfect, labored, unequal, irregular, etc., each of which has 

 its significance to the educated and experienced A^eterinarian. 



Sleep, rumination, pregnancy in cows, etc., modify the respiratory 

 movements even in health. Respiration consists of two acts — inspira- 

 tion and expiration. The function of respiration is to take in 

 oxygen from the atmospheric air, which is essential for the mainte- 

 nance of life, and to exhale the deleterious gas known as "carbon 

 dioxid." 



The frequency of the respiratory movements is determined by 

 observ'ing the motions of the nostrils or of the flanks. The normal 

 rate of respiration for a healthy animal of the bovine species is 

 from 15 to 18 times per minute. The extent of the respiratory sys- 

 tem renders it liable to become affected by contiguity to many parts, 

 and its nervous connections are very important. 



Rapid, irregular, or difficult breathing is known as dyspnea, and 

 the animal in all such cases has difficulty in obtaining the amount of 

 oxygen that it requires. Among the conditions that give rise to 

 dyspnea may be mentioned restricted area of active lung tissue, due 

 to filling of portions of the lungs with inflammatory exudate, as in 

 pneumonia; painful movements of the chest, as in rheumatism or 



